Method for transmitting data from a transmitting station to a receiving station via a radio link, and corresponding receiving station and transmitting station

ABSTRACT

A radio link is set up from a transmitting station to a receiving station for the transmission of data after a time interval has elapsed. The time interval is specific to the transmitting station and has a duration which depends on at least one deterministic quantity.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and hereby claims priority to GermanApplication No. 10321205.1 filed on May 12, 2003, the contents of whichare hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for transmitting data from atransmitting station to a receiving station via a radio link, and to acorresponding receiving station and a corresponding transmittingstation.

2. Description of the Related Art

In radio communication systems that use a CDMA procedure (CDMA: CodeDivision Multiple Access) for subscriber separation, the transmissioncapacity in the uplink (or reverse link) direction, i.e. from asubscriber station to a base station, is limited by the interferencelevel existing at the base station. The interference level can becharacterized by a so-called “noise rise” which is defined as the ratioof the total received power to the power of the thermal noise. The noiserise is influenced by the number of transmitting subscriber stations,the power of the signals of the subscriber stations received at the basestation and other sources that generate noise.

Base stations at which a significant increase in noise rise occurssuffer from instabilities (cell breathing) which can cause deteriorationof transmitted services and reduced cell coverage.

It is therefore essential for the operation of a radio access network,for example, the UTRAN (Universal Terrestrial Radio Access Network) in aradio communication system conforming to the UMTS standard (UMTS:Universal Mobile Telecommunication System), to control the noise rise,in that appropriate restrictions for uplink transmissions are defined bythe network, i.e. by UTRAN.

In controlling noise rise two aspects should be taken into account:

-   -   The mean value of the noise rise should be kept below an upper        limit (a typical value here is 6 dB).    -   The fluctuation of noise rise over time, i.e. the variance of a        noise rise distribution function, should be as small as        possible.

Up to now UTRAN has been able to define the maximum transmission powerof subscriber stations by corresponding signals (3 GPP [3rd GenerationPartnership Program] 25.133v 5.6.0, chapter 6.5), in order to controlthe mean value of noise rise. The signals are generated by a RadioResource Controller (RNC) and transmitted to the subscriber stations viabase stations. The disadvantage of this type of signaling lies inrelatively long signal durations, i.e. signal delays, which preventprecise control of noise rise.

To control the fluctuations in noise rise, a fast power control loop canbe used (3 GPP 25.214v5.4.0, chapter 5.1.2). However, this is unsuitableif the total power received at the base station is not constant. This isthe case, for example, with a transmission of data packets that takesplace not continuously but in radio bursts, through new activesubscriber stations or through a change in a reference value of thereception quality (e.g. SIR [Signal to Interference Ratio]) of asubscriber station.

A further possible way of controlling the fluctuation of noise rise isto use a Medium Access Protocol called a DRAC (Dynamic ResourceAllocation Protocol) (3 GPP 25.331v5.4.0, chapter 14.8 and EP 1033846A1). This protocol is intended to reduce statistically the number ofdata transmissions taking place simultaneously by determining the startof a data transmission for a subscriber station by a random function.

Methods which make possible transmission of data packets with increaseddata rates in the uplink direction are currently being discussed underthe designation “enhanced uplink” (3 GPP TR25.896v0.3.0) in the contextof the standardization project of 3 GPP (3rd Generation PartnershipProject). However, access to a transmission medium by the DRAC protocolis not designed to make possible high data rates for data transmissionin the uplink direction. The maximum data throughput is limited to 512Kbits/s (cf. 3 GPP 25.331v5.4.0, chapter 10.3.3.20).

Known from the document “Scheduled and Autonomous Mode Operation forEnhanced Uplink”, 3 GPP TSG RAN WG1#31, Tdoc R1-03-0284, pages 1-7,XP-002298746, is a method whereby a Node B determines which subscriberstations may transmit in the uplink direction. The start time andduration of the data transmissions of the subscriber stations are fixed.In the decision of Node B as to which subscriber stations havepermission to transmit data, and in the selection of a data rate or atransmission power for these subscriber stations, Node B takes account,for example, of the following parameters: memory status of eachsubscriber station, transmission power limitation of each subscriberstation, channel quality estimation for each subscriber station orpermitted noise rise until attainment of the Rise over Thermal (RoT)limit at Node B.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a method for datatransmission with which a transmitting station can so control its datatransmission that a reduction in the interference level at a receivingstation can be achieved.

In a method according to the invention for transmitting data from atransmitting station to a receiving station via a radio link, the radiolink is set up between the transmitting and the receiving station andthe data transmission begins only after the expiration of a first timeinterval specific to the transmitting station, the duration of whichtime interval depends on at least one deterministic quantity. Throughthe lapse of an individual first time interval up to the start of thedata transmission, a statistical distribution of data transmissions of aplurality of transmitting stations is achieved. In this way theprobability of an accumulation of simultaneous data transmissions of aplurality of transmitting stations and a resulting high interferencelevel at the receiving station is reduced. In addition, the use of atleast one deterministic quantity for determining the duration of thefirst time interval makes it possible to influence in a controlledmanner the start of the data transmission, and therefore also theinterference level, which can be characterized by a noise rise. Areduction in noise rise therefore causes a reduction in interferencelevel and vice versa.

A deterministic quantity is distinguished from a randomly generatedquantity in that a deterministic quantity is already theoretically fixedbefore its measurement or calculation, i.e. repeated determination of adeterministic quantity always leads to the same result under the sameboundary conditions. Deterministic therefore means the opposite ofrandom or stochastic.

If the deterministic quantity is a priority class of the transmittingstation, this has the advantage that different transmitting stations canbe allocated different first time intervals in dependence on theparticular priority class. In this way, therefore, data transmission canbe made possible preferentially for a transmitting station used fortransmitting a time-critical service, for example, an emergency call, ascompared to a transmitting station which transmits, for example, asimple text message.

It is also advantageous if the deterministic quantity is at least onetime-variable parameter which is specific to the transmitting stationand/or the radio link. In this way the start of the data transmissioncan always be adapted to the current conditions of a transmissionchannel or to the specific requirements of the transmitting station. Itis especially preferred if the first time interval depends on acombination of the priority class and the specific parameter.

The at least one time-variable parameter specific to the transmittingstation is preferably a state of a data memory of the data to betransmitted and/or a charge state of an energy source supplying thetransmitting station. If the data memory of the transmitting station isalmost full and/or the battery is almost empty, a shortest possiblefirst time interval can be selected for the transmitting station, toprevent the data memory from overflowing and/or the data transmissionfrom not being completed because the battery is empty.

It is especially advantageous if the at least one time-variableparameter specific to the data link relates to transmissioncharacteristics of a physical channel used for the radio link. Forexample, if the transmitting station requires very little transmissionpower for its data transmission because of good transmissioncharacteristics, a shortest possible first time interval can be used forthat station, since only a small increase in the interference levelresults from its data transmission.

The expiry of the first time interval is advantageously determined bycomparison of a value of a counter with a limit value. Instead of atypical counter which is increased or decreased by a predefinable valueat given time intervals, any other device suitable for determining atime interval may, of course, be used. For example, a capacitor may becharged and in this case the comparison with the limit value consists inmonitoring the charge state of the capacitor.

A shortest possible time interval may be achieved, for example, in thatthe above-described counter is counted more quickly, or in that thelimit value is selected especially low or high in dependence on acounting direction of the counter.

The transmitting station advantageously receives from the receivingstation a value for a minimum duration for the data transmission.

It is useful if the minimum duration depends on the priority class ofthe transmitting station.

It is advantageous if the data transmission is interrupted only afterthe expiry of an individual transmission time interval specific to thetransmitting station, the duration of which depends on the deterministicquantity, while the radio link continues to be maintained. In order toreduce the interference level at the receiving station it isadvantageous, additionally to the individual first time interval whichprecedes the start of the data transmission, to determine a maximumduration of the data transmission in dependence on, for example, thepriority class. A further shortening of the transmission duration independence on the time-variable parameter specific to the transmittingstation can additionally diminish the interference level or the noiserise, or reduce fluctuations.

A preferred embodiment of the invention provides that the radio linkcontinues to exist after an interruption of the data transmission, and acontinuation of the data transmission begins after the expiry of asecond time interval specific to the transmitting station, the durationof which depends on the deterministic quantity.

The transmitting station according to the invention and the receivingstation according to the invention possess all the features that arerequired for executing the method according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the present invention willbecome more apparent and more readily appreciated from the followingdescription of the preferred embodiments, taken in conjunction with theaccompanying drawings of which:

FIG. 1 is a block diagram illustrating a data transmission between atransmitting station and a receiving station;

FIG. 2 is a flowchart of the data transmission between the transmittingstation and the receiving station according to FIG. 1;

FIG. 3 is a graph of the time progression for determining the start ofthe data transmission of the transmitting station according to FIG. 1and of a further transmitting station, and

FIG. 4 is a graph of the time progression of the data transmission, theending of the data transmission and the further start of a datatransmission of the transmitting station according to FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference characters refer to like elementsthroughout.

A transmitting station is any station which can transmit signals. In thefollowing exposition a subscriber station is regarded as thetransmitting station. A subscriber station is, for example, a mobiletelephone or a mobile device for transmitting image and/or sound data,for sending fax, Short Message Service SMS and e-mail communications andfor Internet access. It therefore comprises a general transmittingand/or receiving unit of a radio communication system, in particular abase station.

In the following exposition a base station is regarded as the receivingstation, without being restricted thereto.

A receiving station may, of course, also be a mobile station or anyother station having a receiving device for receiving signalstransmitted via a radio link.

The invention may advantageously be used in any desired radiocommunication system. Radio communication systems are understood to meanany system in which a data transmission takes place between stations viaa radio interface. The data transmission may take place bothbidirectionally and unidirectionally. Radio communication systems are,in particular, any mobile radio system conforming, for example, to theGSM (Global System for Mobile Communication) or the UMTS (UniversalMobile Telecommunication System) standard. Ad hoc networks and futuremobile radio systems, for example, fourth-generation systems, should beunderstood to be included in radio communication systems.

The invention is described below with reference to the example of amobile radio system conforming to the UMTS standard, without, however,being restricted thereto.

FIG. 1 represents schematically a data transmission D from a subscriberstation UE1 to a base station NodeB via a radio link V. The subscriberstation UE1 and the base station NodeB each have at their disposal atransmitting and receiving unit SE1, SE2, and a processor P1, P2 forcontrolling the respective transmitting and receiving unit SE1, SE2 anda respective data transmission. While the radio connection V is beingestablished but before the start of a data transmission D to the basestation NodeB, the base station NodeB transmits to the subscriberstation UE1, for example via a broadcasting channel, a first limit valueG1, a second limit value G2 and a priority class PRIO1 of the subscriberstation UE1. Alternatively, the first and second limit values G1, G2 maybe fixed in advance and stored permanently at the subscriber stationUE1. In this case only the priority class PRIO1 is transmitted to thesubscriber station UE1.

The start of the data transmission D of the subscriber station UE1 isdetermined by the subscriber station UE1 by its processor P1. Of course,the base station NodeB may also determine the start of the datatransmission D by its processor P2 and transmit a correspondinginstruction for the data transmission D to the subscriber station UE1.

The determination of the start of the data transmission D causes a firsttime interval t1 which is specific to the subscriber station UE1 toelapse between the establishment of the radio link V and the start ofthe data transmission D (cf. FIG. 3). The first time interval t1 dependssolely on a deterministic quantity, i.e. in order to determine theduration of the first time interval t1 no random values are used, incontrast to the access procedure known from the DRAC protocol.

The duration of the first time interval t1 depends in this embodiment onthe priority class PRIO1 of the subscriber station UE1 and on at leastone time-variable parameter FP1 specific to the subscriber station UE1and/or to the radio link V, and on the first limit value G1 (see thedescription relating to FIGS. 2 and 3).

The specific parameter FP1 is, for example, a state of a data memory ofthe subscriber station UE1, i.e., for example, a capacity utilizationlevel of the data memory, a charge state of the energy source, forexample, a preferably rechargeable battery, or a transmissioncharacteristic of a physical channel used for the data transmission D,for example, a required transmitting power of the subscriber stationUE1.

The deterministic quantity may, of course, depend on any combination ofspecific parameters.

FIG. 2 shows schematically the logic sequence of the establishment ofthe radio link V up to the start of the data transmission D of thesubscriber station UE1, the data transmission D and an interruption ofthe data transmission D.

In box 201 the establishment of the radio link V and the transmission ofthe first and second limit values G1, G2, of the priority class PRIO1and of a minimum duration Tmin1 of the data transmission D from the basestation NodeB to the subscriber station UE1 takes place. Then, in box202, a main counter Z and a sub-counter Z1 are set to a starting value,for example zero. An iteration variable n is set to the value 1. In box203 the sub-counter is increased by a value PR1, which depends on thepriority class PRIO1. A high priority class causes a greater value PR1than a low priority class and therefore yields a shorter first timeinterval t1 than the low priority class. The first time interval beginswith box 201 and ends when box 206 is reached.

The subscriber station UE1 derives the value PR1 from a table, forexample with reference to the received priority class PR1O1. Thesubscriber station UE1 receives the table, together with updates of thetable, via a broadcasting channel, for example. The value PR1 may, ofcourse, also be transmitted via an individual link from the base stationNodeB to the subscriber station UE1.

In box 204 the value of the main counter Z is formed from the sum of thesub-counter Z1 and the specific parameter FP1. After a comparison of thevalue of the main counter Z with the first limit value G1, a resettingof the sub-counter Z1 and the main counter Z is carried out, if Z<G1, byrunning boxes 203 and 204. If Z>G1 the data transmission D is begun inbox 206.

With the start of the data transmission D a further counter N is set tozero. This counter serves to ensure that the data transmission D has atleast the minimum duration Tmin1. For this purpose the further counter Nis compared in box 207 with the minimum duration Tmin1 and is increasedby 1 in box 208 until the condition N=Tmin1 is fulfilled.

If the further counter N is equal to the minimum duration Tmin1, in box209 the sub-counter Z1 is set to the limit value G1 as the startingvalue and a further iteration variable m is set to the value 1. In box210 the sub-counter Z1 is decreased by a value PR2 determined on thebasis of the priority class PRIO1. This value PR2 may be determined withreference to a table in the same way as the value PR1 used in box 203,or transmitted from the base station NodeB.

In box 211 the value of the main counter Z is calculated by subtractionof the specific parameter FP1 from the sub-counter Z1 and compared inbox 212 with the second limit value G2. If the value of the main counterZ>G2, the counter statuses are again calculated in boxes 210 and 211. IfZ<G2, the data transmission D is interrupted in box 213 and, if furtherdata is waiting for transmission or the radio link has not been ended onthe network side or the subscriber side, the above-described procedurebegins again in box 202.

For a further running of the procedure, or even during a run of theprocedure, new first and second limit values, a new priority class and anew minimum duration of the data transmission may, of course, betransmitted from the base station NodeB to the subscriber station UE1.

The values PR1 and PR2, determined on the basis of the priority classPRIO1 and used to calculate the sub-counter Z1 in boxes 203 and 210,may, of course, be equal or different. In this way different maximumdurations may be fixed for the first time interval t1 and for atransmission time interval t3, which lasts from the start of the datatransmission in box 206 until the interruption of the data transmissionin box 213. Furthermore, different specific parameters FP1 may be usedor combined in boxes 204 and 211. Preferably, however, the same specificparameters FP1 are used or combined in boxes 204 and 211.

Equivalently to the above-described embodiment, the start of the datatransmission may also, of course, be determined by a decrease of thesub-counter Z1 and of the main counter Z resulting from a predefinablestart value, and a failure to meet a limit value. Correspondingly,sub-counter Z1 and main counter Z may be increased until a correspondinglimit value is exceeded, to end the data transmission. Equally,different main and sub-counters may be used for the starting and endingof the data transmission.

The base station NodeB explicitly specifies at least one of the limitvalues G1, G2, while the other limit value G1, G2 may, of course, alsobe specified relative to the explicitly specified limit value G1, G2.

The selection of the limit values G1, G2, or the difference between thelimit values G1, G2 depends, for example, on a noise rise at the basestation NodeB, which is defined by the ratio of the total received powerto the power of the thermal noise. Because the invention makes itpossible to reduce a probability of simultaneous data transmission bydifferent subscriber stations through a statistical distribution of thestart of the data transmission and the duration of the transmission ineach case, the noise rise at the base station NodeB can be controlledand therefore optimized by adaptation of the limit values G1, G2 on thebasis of a measured noise rise.

For example, if the noise rise is greater than a desired referencevalue, e.g. 6 dB, the first limit value G1 may be increased and/or thedifference from the second limit value G2 reduced.

The method according to the invention makes lower signaling demands thanthe DRAC protocol mentioned in the introduction because all thesubscriber stations jointly use the first and second limit values G1,G2, and has shorter signal delays because the limit values G1, G2 arecontrolled directly by the base station NodeB, whereas the signaling ofthe DRAC protocol is controlled by a Radio Resource Controller (RNC)which must first send its signals to a base station for onwardtransmission prior to a transmission to a subscriber station.Furthermore, according to the invention subscriber-specific quantitiesare also used, so that the individual requirements of the subscriberstations can be taken into account for the start and ending of a datatransmission. A subscriber station with good transmission conditions,for example a subscriber station which requires little transmissionpower, can be treated preferentially, i.e. can begin its datatransmission more quickly and/or transmit data for longer, than asubscriber station with poor transmission conditions. In the same way, asubscriber station with an almost full data memory can be givenpreference in order to prevent this subscriber station from having tointerrupt a data flow from higher layers when the data memory is full.

A further advantage of the method according to the invention is that,through the use of a priority class, both a maximum time period up to astart of a data transmission and a maximum duration of the datatransmission can be fixed for each subscriber station.

FIG. 3 represents schematically the behavior of the sub-counter Z1 andthe main counter Z of the subscriber station UE1, and the first limitvalue G1. For a further subscriber station the behavior of acorresponding further sub-counter ZZ1 and of a corresponding furthermain counter ZZ is also shown. The values of the sub-counters Z1, ZZ1increase linearly with time and ensure a maximum duration up to thestart of the respective data transmission. From the steeper gradient ofthe sub-counter Z1 in comparison to the further sub-counter ZZ1, it canbe read off that the subscriber station UE1 has a higher priority classPRIO1 than the further subscriber station.

The particular main counter value Z, ZZ is yielded by addition of therespective sub-counter Z1, ZZ1 to the respective specific parameter FP1,FP2. The subscriber station UE1 already begins its data transmission Dafter the first time interval t1, whereas the further subscriber stationbegins its data transmission only after a longer further time intervalt2. In practice, typical maximum durations of the first and further timeintervals t1, t2 are a few tens of milliseconds.

FIG. 4 represents schematically the course of the data transmission D ofthe subscriber station UE1 and an interruption of the data transmissionD, and a resetting of the counters Z, Z1 after the interruption of thedata transmission D. As can be seen from FIG. 3, the subscriber stationUE1 begins its data transmission D after the expiry of the first timeinterval t1. The data transmission D lasts at least the minimum durationTmin1. Only after expiry of the minimum duration Tmin1 are thesub-counter Z1 and the main counter Z decreased again in dependence onthe priority class PRIO1 and the specific parameter FP1 until the secondlimit value G2 has been reached or passed below. The data transmission Dlasts in total the transmission time interval t3. After the interruptionof the data transmission D the sub-counter Z1 and the main counter Z areincreased again, while the radio link V continues to be maintained,until, after the lapse of a second time interval t4, a continuation ofthe data transmission takes place.

The invention can, of course, also be used if the subscriber station UE1carries out a data transmission to a plurality of base stations. Thisoccurs, for example, in the case of a cell change in so-called softhandover.

In soft handover, the subscriber station UE1 receives a first and secondlimit value and/or a priority class and/or a minimum duration of thedata transmission from each of a plurality of base stations. Thesubscriber station now uses, for example, the values it has receivedfrom the base station with the largest noise rise. Of course, thesubscriber station may also form an optionally weighted mean for thelimit values and/or the priority class and/or the minimum duration fromall the values received. In the same way, the transmissioncharacteristics of a physical channel, or a corresponding mean valueformed across all the physical channels, may be used for the specificparameter.

The invention has been described in detail with particular reference topreferred embodiments thereof and examples, but it will be understoodthat variations and modifications can be effected within the spirit andscope of the invention covered by the claims which may include thephrase “at least one of A, B and C” as an alternative expression thatmeans one or more of A, B and C may be used, contrary to the holding inSuperguide v. DIRECTV, 69 USPQ2d 1865 (Fed. Cir. 2004).

1-12. (canceled)
 13. A method for transmitting data from a transmittingstation to a receiving station via a radio link, comprising:establishing the radio link between the transmitting station and thereceiving station; and starting the data transmission at thetransmitting station only after the transmitting station has detectedexpiration of an individual first time interval specific to thetransmitting station, the individual first time interval having aduration depending on at least one deterministic quantity.
 14. A methodaccording to claim 13, wherein the deterministic quantity is a priorityclass of the transmitting station.
 15. A method according to claim 14,wherein the deterministic quantity is at least one time-variableparameter specific to at least one of the transmitting station and theradio link.
 16. A method according to claim 15, wherein the at least onetime-variable parameter specific to the transmitting station is at leastone of a state of a data memory of the data to be transmitted and acharge state of an energy source supplying the transmitting station. 17.A method according to claim 15, wherein the at least one time-variableparameter specific to the radio link relates to transmissioncharacteristics of a physical channel used for the radio link.
 18. Amethod according to claim 17, wherein the expiration of the first timeinterval is determined by a comparison of a value of a counter with alimit value.
 19. A method according to claim 18, further comprisingreceiving at the transmitting station from the receiving station a valuefor a minimum duration for the data transmission.
 20. A method accordingto claim 19, wherein the minimum duration depends on the priority classof the transmitting station.
 21. A method according to claim 20, furthercomprising interrupting the data transmission, while maintaining theradio link, only after expiration of an individual transmission timeinterval specific to the transmitting station, the individualtransmission time interval having duration depending on thedeterministic quantity.
 22. A method according to claim 21, furthercomprising, after said interrupting of the data transmission and whilethe radio link continues to be maintained, beginning continuation of thedata transmission after expiration of an individual second time intervalspecific to the transmitting station, the individual second timeinterval having a duration which depends on the deterministic quantity.23. A transmitting station capable of transmission to a receivingstation, comprising: means for establishing a radio link between thetransmitting station and the receiving station; and means fortransmitting data from the transmitting station to the receiving stationonly after the transmitting station detects expiration of an individualfirst time interval specific to the transmitting station, the individualfirst time interval having a duration depending on at least onedeterministic quantity.
 24. A receiving station capable of receiving atransmission from a transmitting station, comprising: means forestablishing a radio link between the transmitting station and thereceiving station; and means for transmitting at least one deterministicquantity to the transmitting station, a data transmission from thetransmitting station to the receiving station taking place only afterthe transmitting station detects expiration of an individual first timeinterval specific to the transmitting station, the individual first timeinterval having a duration depending on at least one deterministicquantity.